P. Keleher, CVM: The Coherent Virtual Machine. University of Maryland, cvm version 2.0 ed., July 1997.  Home/Search   Document Not in Database   Summary   Related Articles   Check

.... parallel (BSP) model [32] Most popular programming methodologies for Cosmos fall into two categories [15] The first, distributed shared memory (DSM) systems (for example, TreadMarks [2] from Rice University, Multigrain Shared Memory (MGS) 34] from MIT, and Coherent Virtual Machine (CVM) [19] from University of Maryland) provides a software layer which simulates coherent shared memory between nodes by internally using messaging to move around specific data or referenced memory pages. The second, based on message passing primitives (for example, MPI [22] enforces a shared nothing ....

....As we claim in the introduction, software distributed shared memory and messagepassing algorithms are not optimal for Cosmos platforms. For instance, we ported an efficient SMP radix sort code into a software distributed shared memory package called Coherent Virtual Machine (CVM, version 0. 1) [19] which is an extension of the commercial TreadMarks [2] DSM implementation. The performance of this DSM radix sort is given in Fig. 5. In addition, we took an efficient messagepassing code for radix sort (the reader is referred to [4, 5] for a complete analysis of the algorithm and its ....

P. Keleher, CVM: The Coherent Virtual Machine," 0.1 Ed., University of Maryland, November 1996.

.... described in more detail in [7] Existing programming methodologies for SMP clusters fall into two categories [12] The first, distributed shared memory (DSM) systems (for example, TreadMarks [2] from Rice University, Multigrain Shared Memory (MGS) 25] from MIT and Coherent Virtual Machine (CVM) [18] from University of Maryland) provides a software layer which simulates coherent shared memory between nodes by internally using messaging to move around specific data or referenced memory pages. The second, based on message passing primitives (for example, MPI) enforces a shared nothing ....

P. Keleher. CVM: The Coherent Virtual Machine. University of Maryland, 0.1 edition, November 1996.

.... Parallel (BSP) model [32] Most popular programming methodologies for COSMOS fall into two categories [14] The first, distributed shared memory (DSM) systems (for example, TreadMarks [2] from Rice University, Multigrain Shared Memory (MGS) 34] from MIT and Coherent Virtual Machine (CVM) [19] from University of Maryland) provides a software layer which simulates coherent shared memory between nodes by internally using messaging to move around specific data or cosmos ( kaz mos) noun Greek kosmos c. 1650 1: an orderly harmonious systematic universe 2: a complex orderly self inclusive ....

....As we claim in the introduction, software distributed shared memory and message passing algorithms are not optimal for COSMOS platforms. For instance, we ported an efficient SMP radix sort code into a software distributed shared memory package called Coherent Virtual Machine (CVM, version 0. 1) [19] which is an extension of the commercial TreadMarks [2] DSM implementation. The performance of this DSM radix sort is given in Figure 5. In addition, we took an efficient message passing code for radix sort (the reader is referred to [4, 5] for a complete analysis of the algorithm and its ....

P. Keleher. CVM: The Coherent Virtual Machine. University of Maryland, 0.1 edition, November 1996.

....[Lam79] used in bus based hardware DSMs and simulated a cache with page sized lines and latencies determined by the network used. However, the overheads were significant. In particular, because of the large block sizes, false sharing was a problem. A number of more recent systems [KCDZ94, Kel97] resort to methods (such as diffing and lazy release consistency) that reduce these overheads significantly and, in most cases, yield a respectable speedup. There is also another class of software based DSMs [SFL 94, SFH 98, SGT96] that instrument all loads and stores into shared ....

....the loop sequentially. The scope of this system is relatively more limited than other hardware approaches, although the original design has been recently extended [ZRT99] 22 5. 4 Software DSMs One of the first successful software DSM systems is Treadmarks [KCDZ94] and its offspring, CVM [Kel97] Treadmarks uses the virtual memory hardware mechanism and employs a lazy release consistency model as well as a multiple writer protocol with diffing to achieve good performance. Shasta [SGT96] and Blizzard [SFL 94] were developed later. They rely on code instrumentation instead of the ....

Pete Keleher. CVM: The Coherent Virtual Machine. Technical report, Department of Computer Science, University of Maryland, November 1997.

....Multigrain Shared Memory 1 cosmos ( kaz m os) noun Greek kosmos c. 1650 1: an orderly harmonious systematic universe 2: a complex orderly self inclusive system 3: Cluster Of Shared Memory Nodes 1 UNM Technical Report: EECE TR 98 006 (MGS) 34] from MIT and Coherent Virtual Machine (CVM) [19] from University of Maryland) provides a software layer which simulates coherent shared memory between nodes by internally using messaging to move around specific data or referenced memory pages. The second, based on message passing primitives (for example, MPI [22] enforces a shared nothing ....

....an efficient SMP radix sort code into a software dis 3 Note that the NAS IS benchmark requires that the integers be ranked and not necessarily placed in sorted order. 7 UNM Technical Report: EECE TR 98 006 tributed shared memory package called Coherent Virtual Machine (CVM, version 0. 1) [19] which is an extension of the commercial TreadMarks [2] DSM implementation. The performance of this DSM radix sort is given in Figure 5. In addition, we took an efficient message passing code for radix sort (the reader is referred to [4, 5] for a complete analysis of the algorithm and its ....

P. Keleher. CVM: The Coherent Virtual Machine. University of Maryland, 0.1 edition, November 1996.

....Ethernet. In Figure 2, we present the performance results of the already described Mandelbrot calculation. We compare five different implementations of the algorithm: two Rthreadsbased implementations, a message passing version based on PVM, an implementation in the page based DSM system CVM [6] (Version 0.2) and an implementation in the DSM system Adsmith [9] Version 1.8f) which is closely related to the Rthreads system. 0 20 40 60 80 100 120 140 160 180 1 2 3 4 5 6 7 8 Time in seconds Number of processors Rthreads, single elements CVM PVM Rthreads, line by line ....

....eighties. The original idea dates from Kai Li s IVY system [8] that provides virtually distributed shared memory as extension of the virtual memory management within a single machine implementing sequential consistency. Further page based DSM systems are Mermaid, Munin [10] TreadMarks [1] and CVM [6]. TreadMarks and CVM employ the lazy release consistency model [7] Rthreads do not fall in the class of page based systems (i.e. DSM systems with page or cache line sized coherence blocks) Granularity of data sharing is on basis of objects, i.e. variables of simple data types or variables of ....

P. Keleher. CVM: The Coherent Virtual Machine. University of Maryland, Department of Computer Science, 1996.

....fi dependent on e ff exists, then Log(e ff ) can be retrieved after a failure (by Theorem 1) As a result, the rollback recovery of a process must be consistent. 2 4 Performance Study To evaluate the performance of the proposed logging scheme, we have implemented the logging scheme on top of CVM[4] distributed shared memory system. CVM is written using C and well modularized and it was pretty straightforward to add the logging scheme. For the experiment, we have selected LMW(lazy release consistency multiple writer) protocol, and 11 Figure 6: Amount of the Logged Data for the volatile ....

P. Keleher. CVM: The Coherent Virtual Machine. http:www.cs.umd.eduprojectscvm.

....multicast packet. In case of a filesystem form implementation of the runtime system (see next section) this means only one context switch between user and kernel mode, however. 4 Results To examine and test the proposed DSM cache coherence protocol we ve implemented it into the CVM system [4] and deployed it on a network of UNIX workstations communicating over an IPv6 network, both local and the 6bone 1 . Note that IPv6 itself is not a prerequisite, but merely a chosen characteristic of the used testbed. In the case of 6bone communication two sites were available, both with ....

Pete Keleher. Cvm: The coherent virtual machine. Technical report, University of Maryland, July 1997.

....of these processors. In other words, a software Distributed Shared Memory (DSM) System logically provides a single shared global address space over a physically distributed system using a software layer. This abstraction in software can be provided in several ways such as by user level libraries [1, 5], modification of OS, using compiler support [9] and by a combination of these [2, 3] A survey of DSMs can be found in [6] Our work is in the area of user level software DSMs using VM support (DVSMs) Typically, a user level DSM detects the accesses to the shared location by taking the support ....

Pete Keleher. CVM: The coherent virtual machine, July 1997. University of Maryland.

....used them in studying the performance implications. We performed a detailed classi cation of the memory references made by an application executing in a DVSM system and categorized them as improving or degrading the cache or TLB performance. We instrumented several SPLASH 2 [9] benchmarks, CVM [4] (a DVSM implementation from University of Maryland) MPICH [2] a Message Passing Interface implementation from Argonne National Laboratories) and system libraries like libc, libm etc. using the tracing tools we developed and used the generated traces for trace driven simulation of various cache ....

Pete Keleher. CVM: The Coherent Virtual Machine. Technical report, University of Maryland, Jul 1997.

....4 and Section 5, proposed logging and rollback recovery protocols are presented, respectively, and Section 6 proves the correctness of proposed protocols. To evaluate the performance of the proposed scheme, we have implemented the proposed logging scheme on top of CVM(Coherent Virtual Machine)[12]. The experimental results are discussed in Section 7, and Section 8 concludes the paper. 2 The System Model A DSM system considered in this paper consists of a number of nodes connected through a communication network. Each node consists of a processor, a volatile main memory and a non volatile ....

.... 645.92 117 27997371 5525 WTL 407.29 37 141069 3740 SOR SAT 419.11 152 43500094 9722 WTL 259.01 56 123712 5752 FFT SAT 424.47 189 41068823 9251 WTL 272.64 85 123596 6176 WATER SAT 247.52 20 15177669 2715 WTL 215.15 5 55784 1562 Table 2: Experimental Results the CVM(Coherent Virtual Machine) package [12], which supports the sequential consistency memory model, as well as the lazy release consistency memory models. CVM is written using C and well modularized and it was pretty straightforward to add the logging scheme. The basic high level classes are CommManager class and Msg class which handle ....

P. Keleher. CVM: The Coherent Virtual Machine. http:www.cs.umd.eduprojectscvm.

....Ethernet. In Figure 2, we present the performance results of the already described Mandelbrot calculation. We compare five different implementations of the algorithm: two Rthreadsbased implementations, a message passing version based on PVM, an implementation in the page based DSM system CVM [6] (Version 0.2) and an implementation in the DSM system Adsmith [9] Version 1.8f) which is closely related to the Rthreads system. 0 20 40 60 80 100 120 140 160 180 1 2 3 4 5 6 7 8 Number of processors Rthreads, single elements CVM PVM Rthreads, line by line Adsmith Figure 2. Performance ....

P. Keleher. CVM: The Coherent Virtual Machine. University of Maryland, Department of Computer Science, 1996.

....block buffer modifications until synchronization requires their propagation. Multiple writer protocols is essential for relaxed consistency models to exploit their advantages. The multiple writer protocol has been implemented in some recent software DSM systems such as Munin[4] TreadMarks[ CVM[6], and Brazos[7] 2.3 Delayed Propagation Protocol In software DSMs, it is important to reduce the number of messages exchanged, because sending a message in a software DSM is more expensive than in a hardware DSM. Therefore, in Munin s implementation of release consistency (so called eager ....

P. Keleher, "CVM: The Coherent Virtual Machine", CVM Version 0.2, University of Maryland, available at URL: http://www.cs.umd.edu/¸keleher/dsm.html, May 1997,

.... an illusion of logically shared memory over physically distributed memory, known as a Distributed Shared Memory (DSM) or Shared Virtual Memory (SVM) Recent research projects with DSMs have shown good performance, for example IVY [16] Mirage [10] Munin [3] TreadMarks [2] Quarks [14] and CVM [12]. This model has been shown to give good results for programs that have irregular data access patterns that cannot be analyzed at compile time [17] or indirect data accesses that are dependent on the input data set. DSMs share data at the relatively large granularity of a virtual memory page and ....

P. Keleher. CVM: The Coherent Virtual Machine. University of Maryland, CVM Version 2.0 edition, July 1997.

....proposed logging protocol under the actual system environments, the proposed logging protocol (RSL) and the protocol proposed in [27] SAT) have been implemented on top of a DSM system. In order to implement a sequentially consistent DSM system, we use the CVM (Coherent Virtual Machine) package [13], which supports the sequential consistency memory model, as well as the lazy release consistency memory models. CVM is written using C and well modularized and it was pretty straightforward to add the logging scheme. The basic high level classes are the CommManager class and the Msg class which ....

P. Keleher. CVM: The Coherent Virtual Machine. http://www.cs.umd.edu/projects/cvm.

.... provide an illusion of logically shared memory over physically distributed memory, known as a Distributed Shared Memory (DSM) or Shared Virtual Memory (SVM) Recent research projects with DSMs have shown good performance, for example IVY [1] Mirage [2] Munin [3] TreadMarks [4] Quarks [5] CVM [6], and Strings [7] This paper evaluates the performance of a multithreaded DSM, Strings using three different networking technologies, 10 Mbps Ethernet, 100 Mbps Ethernet and 155 Mbps ATM. The performance of the different configurations are evaluated using programs the SPLASH 2 [8] benchmark ....

P. Keleher, CVM: The Coherent Virtual Machine. University of Maryland, CVM Version 2.0 ed., July 1997.

.... is to provide a view of logically shared memory over physically distributed memory, known as a Distributed Shared Memory (DSM) or Shared Virtual Memory (SVM) Recent research projects with DSMs have shown good performance, for example IVY [1] Mirage [2] Munin [3] TreadMarks [4] Quarks [5] CVM [6], and Strings [7] This model has also been shown to give good results for programs that have irregular data access patterns, which cannot be analyzed at compile time [8] or indirect data accesses that are dependent on the input data set. DSMs share data at the relatively large granularity of a ....

P. Keleher, CVM: The Coherent Virtual Machine. University of Maryland, CVM Version 2.0 ed., July 1997.

....running Ultrix V4.3 over a 100 Mbps ATM network. Near linear speed ups were obtained on a Mixed integer programming problem. A Genetic linkage analysis problem showed good results for data sets with long sequential running times. Recent variants of the TreadMarks system include CVM [46] and Cashmere 2L [47] 4.1.5 Quarks This is another runtime library system that can be linked with an application program [48] A central server is used to initially allocate shared regions and global barriers and locks. It does not pose a bottleneck since it is involved only at program ....

....are shown in the next chapter. 6. Performance Evaluation The evaluation of Strings was done in three parts. The first shows the effect of the various design decisions on the runtime performance. The next part compares the performance with respect to three other DSM systems, CRL [50] CVM [46], and Quarks [48] The final part shows the effect of using different networking technologies on the overall performance of the system. 6.1 Experimental Environment 0000000 0000000 0000000 1111111 1111111 1111111 0000000 0000000 0000000 1111111 1111111 1111111 0000000 0000000 0000000 1111111 ....

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P. Keleher, CVM: The Coherent Virtual Machine. University of Maryland, CVM Version 2.0 ed., July 1997.

....This approach provides an easy programming interface i.e. shared memory, as well as the scalability of distributed memory machines. Page based DSMs use the virtual memory mechanism provided by the operating system, to trap accesses to shared areas. Examples include TreadMarks [1] Quarks [2] CVM [3], and Strings [4] An important aim in DSM design is to minimize the communication requirements Parallel and Distributed Computing Laboratory, Wayne State University, Detroit, MI 48202 of the system. Single writer based systems that use an invalidate protocol to enforce consistency can ....

....describes the experimental environment and the programs used for the evaluation. The results are given in Section 4. Section 5 concludes the paper. 2 SOFTWARE DSM OVERVIEW The DSM systems that were evaluated are the page based systems CVM, Quarks and Strings. 2. 1 CVM: Coherent Virtual Machine CVM [3] is a page based DSM implemented as a user level library which is linked with shared memory programs. The base system provides a generic coherence protocol, user level lightweight threads and reliable network communication on top of UDP. The shared memory system is created by preallocating a large ....

P. Keleher, CVM: The Coherent Virtual Machine. University of Maryland, CVM Version 2.0 ed., July 1997.

....simple programming approach (see Figures 1 and 2) Programming methodologies for COSMOS fall into two categories. The first, distributed shared memory (DSM) systems (for example, TreadMarks [2] from Rice University, Multigrain Shared Memory (MGS) 30] from MIT and Coherent Virtual Machine (CVM) [17] from University of Maryland) provides a software layer which simulates coherent shared memory between nodes by internally using messaging to move around specific data or referenced memory pages. The second, based on message passing primitives (for example, MPI [19] enforces a shared nothing ....

....As we claim in the introduction, software distributed shared memory and message passing algorithms are not optimal for COSMOS platforms. For instance, we ported an efficient SMP radix sort code into a software distributed shared memory package called Coherent Virtual Machine (CVM, version 0. 1) [17] which is an extension of the commercial TreadMarks [2] DSM implementation. The performance of this DSM radix sort is given in Figure 14. In addition, we took an efficient message passing code for radix sort (the reader is referred to [5] for a complete analysis of the algorithm and its ....

P. Keleher. CVM: The Coherent Virtual Machine. University of Maryland, 0.1 edition, November 1996.

....DSM system for workstation clusters is Kai Li s IVY system [6] that provides virtually distributed shared memory as extension of the virtual memory management within a single machine implementing sequential consistency. Further page based DSM systems are Mermaid [7] Mirage [8] Munin [9] CVM [10], SoftFLASH [11] and TreadMarks [12] TreadMarks and CVM employ the lazy release consistency model [4] Due to the architecture of page based systems access to distributed memory is triggered by the virtual memory management. Object based DSM systems, like Midway [13] Shasta [14] Adsmith [15] ....

P. Keleher. CVM: The Coherent Virtual Machine. University of Maryland, Department of Computer Science, 1996.

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P. Keleher, CVM: The Coherent Virtual Machine. University of Maryland, cvm version 2.0 ed., July 1997.

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P. Keleher. (1996, Nov.) CVM: The Coherent Virtual Machine. University of Maryland. [Online]. Available: http://www.cs.umd.edu/projects/cvm/

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Pete Keleher. CVM: The Coherent Virtual Machine. CVM version 0.1. University of Maryland. Nov. 1996.

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P. Keleher, CVM: The Coherent Virtual Machine, University of Maryland, CVM Version 2.0, July 1997.

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